The present invention relates to a photoresist discharge monitoring apparatus. Particularly, the present invention relates to a photoresist discharge monitoring apparatus in which the photoresist discharge rate is monitored during its discharge by a discharge pump, and based on this monitoring, the discharge pump is controlled, so that a constant photoresist discharge rate is ensured, thereby making it possible to prevent any occurrence of process defects due to the discharge pump.
At the photoresist treatment step in the semiconductor device fabricating process, a photoresist is spread on the surface of the treating object such as a wafer to form a photoresist film on it. Then the photoresist film is exposed to a predetermined pattern, and then, a development is carried out by using a certain development fluid.
The spreading of the photoresist is carried out in the following manner. That is, as shown in FIG. 1, the photoresist is discharged from a photoresist-containing vessel 1 by a discharge pump 3 in accordance with pumping signals which are supplied from a spinner control device.
Under this condition, the photoresist is discharged after foreign materials are filtered off by a chemical filter 2, and when the photoresist is discharged by the discharge pump 3, the photoresist passes through a cut-off/suck-back valve 4 and a nozzle 5 to be spread on a wafer 6.
When the photoresist is discharged by the discharge pump 3, the photoresist is discharged at a constant rate. However, if a facility malfunction occurs, or if the life expectancy of the chemical filter 2 has been exhausted to the degree of a filtering failure, then the photoresist cannot be spread to a proper degree, with the result that a wafer defect occurs.
The present invention is intended to overcome the above described disadvantage of the conventional technique.
Therefore it is an object of the present invention to provide a photoresist discharge monitoring apparatus in which the photoresist discharge rate is monitored during its discharge by the discharge pump, and based on this monitoring, the discharge pump is controlled so as to ensure a constant discharge rate of the photoresist.
It is another object of the present invention to provide a photoresist discharge monitoring apparatus in which if the photoresist discharge rate is decreased due to the exhaustion of the life expectancy of the chemical filter, a filter replacement necessity is displayed, thereby making it possible to prevent any occurrence of process defects.
In achieving the above objects, the photoresist discharge monitoring apparatus used in discharging a photoresist from a photoresist-containing vessel by driving a discharge pump and a step motor according to the present invention includes: a PR (photoresist) discharge rate sensor for sensing the photoresist discharge rate, the discharge rate being decided by the discharge pump; and a PR discharge rate controller for monitoring the output signals of the PR discharge rate sensor to automatically control the photoresist discharge rate of the discharge pump, and for judging a chemical filter replacement necessity upon an arrival of an operating limit in the step motor so as to output filter replacement signals.
The PR discharge rate controller includes: a PR discharge rate calculating part for calculating the photoresist discharge rate of the discharge pump based on pulses of the PR discharge rate sensor; a PR discharge rate control part for sending the pumping control signals to the discharge pump based on calculated values of the PR discharge rate calculating part to control the step motor so as to automatically control the photoresist discharge rate, and for outputting the filter replacement necessity signals by judging on the filter replacement necessity upon arrival of the operating limit in the step motor; and a display part for displaying the filter replacement necessity signals and other signals from the PR discharge rate control part.